Current methods for producing man-made diamond entail producing diamond either by chemical vapor deposition (CVD) or high pressure/high temperature (HP/HT) methods. CVD methods of fabricating diamond are derived from the physical methods and equipment used by the semiconductor industry. But, adapting similar or existing equipment and infrastructure does not necessarily lead to the most efficient and effective means of producing diamond films. CVD methods are inefficient because they typically rely on high temperature conditions and surface kinetics with the objective that carbon atoms will assemble into diamond or diamond-like materials. This relies on atomic motion, which can be chaotic and unpredictable. The original conception of HP/HT methods for making diamond was likely based on the brute force approach of emulating the geological processes by which diamond is produced in nature. But, nature doesn't typically produce pure diamond, much less pure diamond films that are useful industrially or commercially. Thus, current physical methods for producing diamond are inefficient and costly because they depend on surface kinetics and/or extreme process conditions for the production of diamond rather than a thermodynamically driven synthesis that could favor the specific production of molecular diamond, i.e., the diamond unit cell. Further, current methods of producing diamond also tend to be inefficient and uneconomical because they require many hours, if not days, to produce diamond films sufficiently thick to be of any practical use.
Moreover, diamond produced by current and conventional methods is typically impure, which prevents its use in many potential applications. To improve the purity of conventionally made diamond, additional processes and steps (for example, high temperature annealing), are required which is costly in terms of time and money, often making such diamond products economically unfeasible for most applications. A further limitation is that many substrate materials upon which diamond could be deposited are precluded from use because they are incompatible with the extreme conditions typically required conventional diamond-forming methods, such as high temperatures and pressures.
Current methods of diamond production are also limited because diamond deposition on the substrate cannot be controlled according to its location on a substrate. These methods typically are limited because they produce films that are essentially “sheets” of diamond that form at random in a deposition space. Thus, current methods do not disclose how to deposit diamond at a predetermined location or locations on a portion of, or in relation to, the substrate either at a planar position of the substrate or vertically upon a previously deposited diamond mass. Thus, conventional methods cannot neither provide for a controllable deposition of diamond mass three-dimensionally nor can they controllably deposit a diamond mass three-dimensionally to produce predetermined, complex shapes. Furthermore, current methods do not disclose a controlled delivery of reactants for the combinatorial synthesis of the diamond unit cell such that a diamond mass can be controllably formed to produce a predetermined three-dimensional shape at a predetermined location. In particular, they do not disclose the controlled delivery of reactants by the use of a dispenser that targets a predetermined location for deposition. They also do not teach controlling the deposition of diamond by starting, stopping, and re-starting the diamond deposition process as a means of controlling morphology. Indeed, given the relatively long time necessary for conventional methods to deposit diamond on a substrate, this would be counterintuitive and counterproductive.
Indeed, current methods for producing diamond cannot be easily adapted to the requirements and demands of widely differing applications nor can they be implemented using different apparati that are specifically designed to efficiently produce diamond-based products for specific uses. Current methods that use CVD to produce diamond films cannot produce them efficiently or quickly, and methods that rely on HP/HT approaches cannot produce bulk diamond in large quantities or in a great variety of complex shapes. In fact, no current method for producing diamond enables the production of diamond of predetermined size and/or complex shape through the use of molds into which reactants are dispensed or injected. A representative sampling of current methods and their limitations are noted below.
U.S. Pat. No. 4,849,199 discloses a method for suppressing the growth of graphite and other non-diamond carbon species during the formation of synthetic diamond. This method includes vaporizing graphite or other non-diamond carbon species with incident radiative energy that doesn't damage the substrate. Use of laser energy is also disclosed. This patent clearly evidences the major problem of contaminating graphitic impurities formed when using conventional diamond forming processes.
US 2014/0150713 discloses controlled doping of synthetic diamond material. During the disclosed diamond growth process using a CVD technique, dopant gases, including one or more of boron, silicon, sulphur, phosphorus, lithium and/or nitrogen are introduced into the plasma chamber. This patent describes that in the region where diamond is metastable compared to graphite, synthesis of diamond under CVD conditions is driven by surface kinetics and not bulk thermodynamics.
Additionally, WO8802792 discloses a process for depositing layers of diamond and describes that the reaction to deposit graphite competes with that to deposit diamond, and under many conditions graphite rather than diamond is deposited. Once deposited, the diamond is energetically favored to convert to graphite, but the reverse reaction of conversion of graphite to diamond is not thermodynamically favored.
US 2011/0280790 discloses production of large, high purity single crystal CVD diamond. Their diamond is grown using a plasma assisted chemical vapor deposition technique at growth temperatures of about 1250 to 1350° C. with growth rates of up to 200 μm/hour.
U.S. RE41,189 discloses a method of making enhanced CVD diamond. In this method, CVD diamond is heated to temperatures between 1500° C. and 2900° C. at a pressure of 4.0 GPa to prevent significant graphitization and with some improvement in the optical properties of the diamond produced.
U.S. Pat. No. 5,284,709 discloses a two-stage, plasma CVD deposition process, and the detrimental effects of structural and chemical inhomogeneities on the phonon-mediated thermal conductivity of diamond. Thus, impure, structurally non-uniform diamond is not optimally effective as a heat transfer material.
U.S. Pat. No. 5,270,077 describes the production of diamond films on convex substrates while U.S. Pat. No. 5,776,246 discloses the production of diamond films on convex or concave substrates to compensate for stress and distortions in the diamond film that can cause cracking and other imperfections.
U.S. Pat. No. 5,507,987 discloses a method of making a freestanding diamond film with reduced bowing. The method entails depositing two different layers of diamond each at different deposition rates.
U.S. Pat. No. 6,319,439 discloses a method of synthesizing diamond film without cracks which entails the use of an artificially compressive stress while decreasing the deposition temperature in a step-wise fashion.
US 2014/0335274 discloses use of a mold to define the deposition of nano-diamond particles on a substrate. This is done merely to define the placement of a nano-diamond seed solution for subsequent formation of a diamond structure, which can be accomplished, as disclosed therein, according to methods for growing diamond on a diamond seed structure as known in the art.
U.S. Pat. No. 7,037,370 discloses freestanding diamond structures and methods. The produce a diamond layer “formed by chemical vapor deposition (CVD) over the surface of a substrate that has been fabricated to form a mold defining the sub-set of intersecting facets.” This patent also discloses the use of high temperature and high pressure methods.
U.S. Pat. No. 7,132,309 discloses semiconductor-on-diamond devices and methods of forming them where a mold is provided which has an interface surface configured to inversely match a configuration intended for the device surface of a diamond layer. However, only vapor deposition techniques for depositing diamond are disclosed and these techniques do not employ a chemical synthesis reaction that is thermodynamically driven to produce molecular diamond.
The diamond-based substrate for electronic devices, of U.S. Pat. No. 7,842,134 is grown by CVD on a silicon wafer.
Hence, in view of the many shortcomings of the conventional methods described above, a need remains for methods for producing diamond in a controllable manner without using diamond seeds or extreme reaction conditions of high temperature and high pressure. A need also continues to exist for methods of producing diamond that do not require one or more subsequent annealing steps to reduce impurities and imperfections in the diamond initially produced. A need also continues to exist for methods for producing diamond that allow for the controlled deposition of diamond mass in predetermined complex shapes.